The present invention relates to a fluid delivery mechanism for the delivery of liquids and other fluids.
Fluid delivery mechanisms are known in the art. Positive displacement pumps are one category of fluid delivery mechanisms that operate on a flexible tube to generate a pumping action. One category of positive displacement pumps that operate on the flexible tube are also known as valve-type pumps. In the operation of the valve-type pump, a plunger compresses the flexible tube thus forcing a liquid contained in the flexible tube out of the flexible tube.
One such application for the positive displacement pump is the administration of intravenous liquids. The administration of intravenous liquids to a patient is well known in the art. Typically, a solution such as saline, glucose or electrolyte contained in a flexible container is fed into a patient""s venous system through a conduit such as a polyvinyl chloride (PVC) tube which is accessed to the patient by a catheter. Many times, the fluid is infused under the forces of gravity, and the rate of flow is controlled by a roller clamp which is adjusted to restrict the flow lumen of the tube until the desired flow rate is obtained.
Flow from the container to the patient also is known to be regulated by means other than a roller clamp. It is becoming more and more common to use an electronically controlled infusion pump. Such pumps include, for example, valve-type pumps. In such devices, a container or bag typically provides for the delivery of the fluid to the tube. A mechanism pinches on the tube using an occluder, and typically a pair of occluders. A plunger, pressing on the tube between the occluders provides the motive force to deliver fluid to the patient. When fluid is delivered to a patient, one of the occluders opens. Different bolus sizes are accomplished by controlling a stroke distance of the plunger. Different flow rates are accomplished by varying the frequency of the operation of the occluders and plungers open/close cycle.
One disadvantage of the prior art infusion pumps is that the operation of an occluder and/or a plunger on the tube will eventually deform the tube and change the pumping volume. This disadvantage may arise for many reasons. The operation of the occluder or the plunger may stretch the tube thus changing the volume contained within the tube. The operation of the occluder or the plunger may cause the tube to permanently set in a shape that also results in a changed volume contained within the tube. Therefore, over time, such devices become less accurate as to the amount of liquid delivered to a patient. While mechanical devices have been designed that return the tube to its original shape between pumping cycles, such devices do not completely eliminate the inherent inaccuracy in the valve-type pumps.
What is needed is a medical infusion pump which improves the accuracy of valve-type pumps. What is also needed is a medical infusion pump that does not lose accuracy of bolus delivery the more times the pump is used. What is further needed is a medical infusion pump that offers these advantages yet uses standard tubing and is readily adaptable for use in multiple clinical settings.
The present invention provides a fluid delivery mechanism which improves the accuracy of valve-type pumps. The present invention provides a fluid delivery mechanism that does not lose accuracy of bolus delivery the more times the pump is used. The present invention provides a fluid delivery mechanism that controls the shape of the tubing throughout the pump cycle. The present invention also provides a fluid delivery mechanism that is readily adaptable to use in multiple clinical settings. The present invention further provides a fluid delivery mechanism that is readily adaptable to multiple pump settings.
The present invention provides a fluid delivery mechanism for providing a flow of a deliverable fluid through a tube. Examples of the deliverable fluid are a liquid and a medical liquid. The fluid delivery mechanism includes at least two occluders having an open position and a closed position for releasably pinching-off the tube. A tube portion between the two occluders forms a metering chamber. A first plunger and a second plunger are provided, each plunger having an open position and a closed position for releasably compressing the metering chamber. In the method of the present invention, an occluder releasably pinches-off the tube near the source of the liquid at a first location. The second occluder releasably pinches-off the tube at a second location that is downstream from the source of the liquid and the first location. The tube is released at the first location and a plunger compresses the tube between the first location and the second location, thereby generating a flow of the liquid through the tube in a direction towards the source of liquid.